The present invention relates to a communication system including a network formed by a plurality of control units.
The number of electronic control units (ECUs) installed in a vehicle has been increasing over these recent years. An in-vehicle communication network is formed so that data can be shared between the ECUs. In the in-vehicle communication network system of the prior art, when a single ECU transmits a communication frame on the network, the communication frame is shared by the other ECUs of the network. When an ECU determines that the communication frame is related to the ECU, the ECU performs a process that is in accordance with the communication frame.
Japanese Laid-Open Patent Publication Nos. 2006-42310 and 2007-30714 each disclose a technique that uses a network management frame, which differs from the communication frame described above, to manage a plurality of ECUs forming a network in a wake state (high power consumption mode) and a sleep state (low power consumption mode).
However, in the techniques disclosed in the above publications, the ECUs are switched between wake and sleep states in accordance with the network. That is, the ECUs forming a single network are all simultaneously switched at the same timing to a wake state or a sleep state. Although only one of the ECUs in a network requires being in a wake state to execute vehicle control, the other ECUs in the same network, which are unrelated to the executed vehicle control, are also all shifted to a wake state. This consumes unnecessary power.